Formula One team owner Frank Williams has admitted that rivals McLaren are pursuing his driver Juan Pablo Montoya.

The BBC Sport website revealed this week that McLaren wanted to sign the Colombian after his Williams contract expires next year - or even for 2004 if possible.

Williams said on Sunday: "Juan has a contract with this company until the end of '04 - after that it is an open market.

"We'd love to see him stay with us forever, but I repeat it is an open market and other teams, including McLaren we believe, are after him.

"Humans always tend to think the grass is greener somewhere else. I really don't know which way he is going to jump."

McLaren are believed ideally to want Montoya for 2004 in place of David Coulthard and negotiations are understood to have been continuing over the German Grand Prix weekend.

A source close to the talks has told the BBC that McLaren are offering the Colombian a far bigger salary than he is receiving at Williams, but that Williams have set a high price for McLaren to buy him out of his contract.

Williams gave Montoya his break in F1 but relations between the team and their driver have deteriorated this season.

Montoya is said to be unhappy at the salary disparity between himself and team-mate Ralf Schumacher.

Montoya is said to be on a salary of only $2.5m (£1.6m), while Schumacher is on $12m (£7.5m) this season, rising to $15m (£9.4m) in 2004.

Juan is frustrated that it isn't happening for him. We're working hard with him to work out why

"I am feeling very good at Williams at the moment. I have got one more year here until the end of '04 but then we will see what happens," he said.

"I am a free agent after 2004. If I changed team then it wouldn't be for money. It is not about getting paid. I do it because I love it."

Ferrari's Rubens Barrichello and Jordan driver Giancarlo Fisichella are said to have held talks about a move to Williams.

Williams are understood to believe Montoya is not delivering on his enormous potential, and the 27-year-old was upset by the team's refusal to help him beat team-mate Ralf Schumacher at the French Grand Prix last month.

Montoya has been overshadowed by Schumacher for much of this season and has been out-qualified eight times in 12 races.

Williams have recently taken steps to ensure Montoya is able to get more out of his car a race weekends.

"One would have to say that Juan and his engineering team supporting him are not doing as good a job as Ralf and his engineering team supporting him and we have to work out how to put it right," Williams technical director Patrick Head told the BBC Sport website.

"Somehow Ralf seems to be able to get more out of the car than Juan can now."

Head added: "He's frustrated that it isn't happening for him. We're working hard with him to work out why. When we open the right pigeon hole, maybe he will start putting strings of race wins together."